pulling my hair out!!!

Hi all.

I've just introduced myself in the new members area but thought i'd post my question to try and get to the bottom of my problem.

I have a 54 reg A6 3.0TDI which i have owned for nearly 2 years and to be honest it's been in the garage for at least a third of that time.

My problems started with the MIL light coming on occasionally but the car still drove fine. It then suddenly lost all boost and went into limp home mode. I took it to my local garage who plugged it in and cleared the codes for me. It did it again the following day so i bought a cheap fault reader. It was rather sporadic and could go weeks without it happening at all or do it 3 times in an hours journey.

Long story short when it got to the point where it wasn't clearing i bit the bullet and had a new turbo fitted. 

The code i'm getting is P0046 - turbocharger/supercharger boost control solenoid A circuit.

I've done loads of research on this on the net with no definitive answer. I've replaced the turbo and actuator, boost sensor (twice), pressure switch and recently the MAF sensor and i'm still getting no boost.

I believe it has been remapped at some point. I've stopped using it as of last august as it's just painful trying to get up the hills on my way too work and looking to sell the car but would obviously rather sell it working than not.

Has anyone had any similar problems or have any ideas on where my next step might be. I've gone from loving this car to hating it.

Thanks in advance

Darren